1. Technical Field of the Invention
The present invention relates to stators for electric rotating machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of the Related Art
Conventionally, there are known stators for electric rotating machines which include a hollow cylindrical stator core and a stator coil. The stator core has a plurality of slots that are formed in the radially inner surface of the stator core and spaced in the circumferential direction of the stator core. The stator coil is comprised of a plurality of electric wires mounted on the stator core.
Moreover, there is disclosed, for example in Japanese Unexamined Patent Application Publication No. 2001-145286, a method of manufacturing a stator. According to the method, to improve the space factors of the electric wires in the slots of the stator core, each of U-phase, V-phase, and W-phase windings of the stator coil is configured to have a rectangular cross section and have such an overall shape that when developed on a plane, the winding meanders in the form of cranks. Further, each of the U-phase, V-phase, and W-phase windings is wound by a predetermined number of turns into a spiral shape, so as to make the stator coil have a hollow cylindrical shape.
With the above method, however, each of the electric wires (or electric conductors) that respectively make up the U-phase, V-phase, and W-phase windings of the stator coil is required to have a long length. Accordingly, a large-scale shaping machine is needed for shaping the electric wires. Moreover, since each of the electric wires is long, it is difficult to handle the electric wires during the manufacture of the stator. As a result, it is difficult to secure a high productivity and a low cost of the stator. Furthermore, since the electric wires are wound into the spiral shape and received in the slots of the stator core, interference may occur, due to the springback of the electric wires, between the stator coil and a rotor disposed radially inside of the stator. Consequently, the stator coil may be damaged due to this interference, thereby lowering the reliability of the stator.